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Yeah, I have worked with FPGAs a while ago and still casually follow the space.

There have been many attempts of mapping general purpose/GPU programming languages to FPGA and none of them worked out.

The first leading claim they make - that this is a general purpose CPU, capable of executing anything - I suspect is false.

CPUs are hard because they have to interact with memory, basically 95% of CPU design complexity comes from having to interact with memory, and handling other data hazards.

If this was reducible complexity, they'd have done so already.

I recall Mathstar's FPOA (field programmable object arrays) have had similar architecture. it seems they have done a mixture of stack computer, this and some async programming to get this level of optimization. The other one I had seen with pretty good on chip fabric was Tilera who were using something like a packet switch to interconnect tonnes of on-chip cores.

My first reaction watching this video was that they are just shifting the problem to compiler, which is actually worse and also does not works for dynamic code with tonnes of branches. Also, didnt Intel burn a lot of money trying to do this with Itanium?

Overall, interesting idea but I filed it under 'solution looking for a problem' desk.

I agree this is very "FPGA-shaped" and I wonder if they have further switching optimisations on hand.

My understanding is that they have a grid configuration cache, and are certainly trying to reduce the time/power cost of changing the grid connectivity.

That was my first thought too. I really like the idea of interconnected nodes array. There's something biological, thinking in topology and neighbours diffusion that I find appealing.

Sure. You can think of a (simple) traditional CPU as executing instructions in time, one-at-a-time[1] — it fetches an instruction, decodes it, performs an arithmetic/logical operation, or maybe a memory operation, and then the instruction is considered to be complete.

The Efficient architecture is a CGRA (coarse-grained reconfigurable array), which means that it executes instructions in space instead of time. At compile time, the Efficient compiler looks at a graph made up of all the “unrolled” instructions (and data) in the program, and decides how to map it all spatially onto the hardware units. Of course, the graph may not all fit onto the hardware at once, in which case it must also be split up to run in batches over time. But the key difference is that there’s this sort of spatial unrolling that goes on.

This means that a lot of the work of fetching and decoding instructions and data can be eliminated, which is good. However, it also means that the program must be mostly, if not completely, static, meaning there’s a very limited ability for data-dependent branching, looping, etc. to occur compared to a CPU. So even if the compiler claims to support C++/Rust/etc., it probably does not support, e.g., pointers or dynamically-allocated objects as we usually think of them.

[1] Most modern CPUs don’t actually execute instructions one-at-a-time — that’s just an abstraction to make programming them easier. Under the hood, even in a single-core CPU, there is all sorts of reordering and concurrent execution going on, mostly to hide the fact that memory is much slower to access than on-chip registers and caches.

Found this video a good explanation. https://youtu.be/xuUM84dvxcY?si=VPBEsu8wz70vWbX4

Instead of large cores operating mostly independently in parallel (with some few standardized hardwired pipeline steps per core), …

You have many more very small ALU cores, configurable into longer custom pipelines with each step more or less as wide/parallel or narrow as it needs to be for each step.

Instead of streaming instructions over & over to large cores, you use them to set up those custom pipeline circuits, each running until it’s used up its data.

And you also have some opportunity for multiple such pipelines operating in parallel depending on how many operations (tiles) each pipeline needs.

Probably not. This is graduate-level computer architecture.

I would not expect that this becomes competitive against a low power controller that is sleeping most of the time, like in a typical wristwatch wearable.

However, the examples indicate that if you have a loop that is executed over and over, the setup cost for configuring the fabric could be worth doing. Like a continuous audio stream in a wakeup-word detection, a hearing aid, or continous signals from an EEG.

Instead of running a general purpose cpu at 1MHz the fabric would be used to unroll the loop, you will use (up to) 100 building blocks for all individual operations. Instead of one instruction after another, you have a pipeline that can execute one operation in each cycle in each building block. The compute thus only needs to run at 1/100 clock, e. g. the 10kHz sampling rate of the incoming data. Each tick of the clock moves data through the pipeline, one step at a time.

I have no insights but can imagine how marketing thinks: "let's build a 10x10 grid of building blocks, if they are all used, the clock can be 1/100... Boom - claim up to 100x more efficient!" I hope their savings estimate is more elaborate though...

Human interfaces, sure, but there's a good chunk of industrial sensing IoT that might do some non-trivial edge processing to decide if firing up the radio is even worth it. I can see this being useful there. Potentially also in smart watches with low power LCD/epaper displays, where the processor starts to become more visible in power charts.

Wonder if it could also be a coprocessor, if the fabric has a limited cell count? Do your dsp work on the optimised chip and hand off the the expensive radio softdevice when your codesize is known to be large.

I thought the same thing :-)

Out of order cores spend an order of magnitude more logic and energy than in-order cores handling invalidation, pipeline flushes, branch prediction, etc etc etc... All with the goal of increasing performance. This architecture is attempting to lower the joules / instruction at the cost of performance, not increase energy use in exchange for performance.

Was I misreading, or is this thing not essentially unclocked? There have been asynchronous designs in the past (of ARM6 cores, no less) but they've not taken the world by storm.

there are orders of magnitudes more embedded processor sales than desktop CPUs.... So the answer really is... lots of people will want it.

Curios what you mean by 3D and also how 3D is used. Assuming something like [0] I can pretty confidently tell you that it is not 3D as it is a low power microcontroller and this technology is mostly used in large expensive HPC/AI chips also afaik 3D stacking of logic die is not really a thing (if anyone knows counterexamples pls provide) it is much more common for stacking memory die ex HBM. As for your proposed coprocessor that actually might benefit from 3D integration with the trad cpu as >> # of interconnect / memory channels could allow you to route data more directly to processing elements. Something like this is proposed with “2.5D” stacking in [1] where HBM (3D) is connected to an FPGA with 128 channels.

[0] https://resources.pcb.cadence.com/blog/2023-2-5d-vs-3d-packa...

[1] page 6: https://bu-icsg.github.io/publications/2024/fhe_parallelized...

Perhaps instead you are referring to the program graphs and whether they are better represented as hyper graphs [0] with certain regular edges within a 2D layer and hyper edges between 2D layers? If so, good question and I am not sure if the answer, I agree that it would probably be a helpful abstraction layer to assist with certain data locality and reduce data movement + congestion issues. [0] https://lasttheory.com/article/what-is-a-hypergraph-in-wolfr...

The Mill videos are worth watching again - there are variations on NaT handling and looping and branching etc that make DSPs much more general-purpose.

I don’t know how similar this Electron is, but the Mill explained how it could be done.

Edit: aha, found them! https://m.youtube.com/playlist?list=PLFls3Q5bBInj_FfNLrV7gGd...

It kinda sounds like it, though the article explicitly said it's not VLIW.

I've always felt like itanium was a great idea but came too soon and too poorly executed. It seemed like the majority of the commercial failure came down to friction from switching architecture and the inane pricing rather than the merits of the architecture itself. Basically intel being intel.

On the other hand, Groq seems pretty successful.

I think this is more like an fpga than simply a bunch of cores arranged in a fabric.

This is essentially a CGRA (Coarse-Grained Reconfigurable Array) architecture, which historically has shown impressive efficiency in academic research but struggled with compilation complexity and commercial adoption precisely because of the NP-hard routing problems you've identified.

> The need to do routing etc. reminds me of the problems FPGAs have during place and route (effectively the minimum cut problem on a graph, i.e. NP)

I'd like to take this opportunity to plug the FlowMap paper, which describes the polynomial-time delay-optimal FPGA LUT-mapping algorithm that cemented Jason Cong's 31337 reputation: https://limsk.ece.gatech.edu/book/papers/flowmap.pdf

Very few people even thought that optimal depth LUT mapping would be in P. Then, like manna from heaven, this paper dropped... It's well worth a read.

Yep, or the old GreenArrays GA144 or even maybe XMOS with more compiler magic.

One of the big questions here is how quickly it can switch between graphs, or if that will be like a context switch from hell. In an embedded context that's likely to become a headache way too fast, so the idea of a magic compiler fixing it so you don't have to know what it's doing sounds like a fantasy honestly.

The 2022 PhD thesis linked from their web site includes a picture of what they claim was an actual chip made using a 22nm process. I understand that the commercial chip might be different, but it is possible that the measurements made for the thesis could be valid for their future products as well.

There's >20 years of academic research behind dataflow architectures going back to TRIPS and MIT RAW. It's not literally a scam but the previous versions weren't practical and it's unlikely this version succeeds either. I agree that if the compiler was good they would release it and if they don't release it that's probably because it isn't good.

I like Ian but he’s rapidly losing credibility by postings so much sponsored content. Many of his videos and articles now are basically just press releases.

I think it's more like having the instructions your program does spread accross mulitple tiny processors.

So one instruction gets done.. output is pass to the next.

Hopefully i've made somebody mad enough to explain why i am wrong.

This has nothing to do with mainframes (which are fairly normal general purpose computers).